A general object of the present invention is to provide a sprung suspension arrangement by means of which one or more wheels may be independently suspended from a trailer frame. Another object of the invention is to provide a suspension system of the described character in which the one or more wheel suspension arrangements are independently mountable, demountable and/or adjustable with respect to the trailer frame. Yet another object of the invention is to provide a suspension system of the described character in which the height of each wheel suspension is independently adjustable with respect to the trailer frame and with respect to the other wheels. A further object of the invention is to provide a suspension system of the described character in which the camber and toe-in at each wheel is independently adjustable.
A demountable suspension system for a trailer in accordance with one aspect of the present invention includes a suspension arm having a spindle at a first end for rotatable mounting of a vehicle wheel. The suspension arm is pivotally mounted on a support at a second end of the arm spaced from the first end. A suspension spring system is operatively coupled between the suspension arm and the support to resist pivotal motion of the arm with respect to the support. The suspension arm support, suspension arm and spring system are all selectively mountable and demountable as a unit to a trailer frame. Pivotal position of the suspension support arm with respect to the support is selectively adjustable by adjusting the anchor point of the spring system to either the suspension arm or the arm support. In various embodiments of the invention, the spring system comprises a torsion bar spring, a coil spring, a plurality of leaf springs or a shock absorber nested within a coil spring.
A torsion bar suspension system for a trailer having a trailer frame in accordance with one particularly preferred embodiment of the invention includes a suspension arm having a spindle at one end for rotatably carrying a wheel. The suspension arm is mounted to the trailer frame to pivot about an axis spaced from the wheel axis of rotation. A torsion bar is mounted to the trailer frame between the wheel end of the suspension arm and the suspension arm pivot axis. The torsion bar is operatively coupled to the suspension arm such that torque at the torsion bar resists pivoting of the suspension arm about its pivot axis. The torsion bar/suspension arm coupling comprises an arm of variable length to accommodate changing radius between the torsion bar and the suspension arm as the suspension arm rotates about its pivot axis.
The torsion bar/suspension coupling arm in the preferred embodiment of the invention is fastened at one end to the torsion bar and at an opposing end to a nut having threads received on an adjustment screw. The adjustment screw is fastened to the suspension arm and is rotatable with respect thereto about an axis that is orthogonal to the pivot axis of the suspension arm. Rotation of the screw and consequent motion of the nut along the screw body thereby adjusts height of the suspension arm and wheel with respect to the trailer frame.
The suspension arm and torsion bar are selectively mountable and demountable as an assembly to and from the trailer frame. The trailer frame includes laterally spaced supports, and the suspension system is mounted to the supports by an inboard mounting bracket to which the torsion bar is affixed, and an outboard mounting bracket through which the torsion bar rotatably extends. Preferably, a brace is affixed to the inboard and outboard mounting brackets to hold the brackets at parallel positions spaced from each other corresponding to lateral spacing between the inboard and outboard trailer frame supports. The brackets are selectively demountable from the trailer frame for adjusting position of the suspensions and wheels with respect to the frame as a function of trailer load.